Running Economy

There are several components that make up running ability, including V̇O2max, and economy. V̇O2max is the ability of our bodies to generate energy for running and is the focus of a lot of our training. Running Economy is how far and fast you can run with a given amount of energy. Good economy is a critical part of running, and Cadence is one element I recommend runners focus on. (For the financial cost of running, see The Cost of Running.)

1 The Importance of Improving Running Economy

Running Economy can vary by as much as 30% between runners of a similar V̇O2max[1]. The two charts below show the V̇O2max and running economy of Paula Radcliffe over a 10 year period[2]. Over that time Paula Radcliffe's race performance dramatically improved even though her V̇O2max did not. This suggests that for elite athletes at least, improvements in running economy are critical.

3 Measuring Running Economy

In an ideal world, we'd be able to easily measure our Running Economy and see if things are improving. If we could measure our breath, find out how much O2 we consumed and how much CO2 we produce, we'd know how much energy we burned (and from fat or carbohydrate). Such testing would require controlling the time of day, day of the week, diet, and footwear for each test[4] as well as specialist equipment that is not available to recreational runners. Because this is not practical, the best measure we have of energy consumption is our Heart Rate. This is far from perfect, as Heart Rate can vary for other reasons besides supplying O2 for energy production. However, I believe it is a useful approximation and so I developed the simpler "Relative Running Economy."

4 Relative Running Economy

Given the difficulty of measuring Running Economy, I have developed a simple alternative that provides a relative value for Running Economy. This Relative Running Economy calculates a value based on how many heart beats are used for the distance covered. The formula that is shown below and there are more details at Relative Running Economy.

Total Beats = (Average Heart Rate – Resting Heart Rate) * Time in Minutes
Work Per Mile = Total Beats / Distance in Miles
Efficiency = 1 / Work Per Mile * 100,000

Note that the difference between Heart Rate and Resting Heart Rate is used to calculate the heart beats used for movement. Ideally the Heart Rate for standing would be used, but typically Resting Heart Rate is taken seated or lying down.

5 How to use Relative Running Economy

The calculated Relative Running Economy cannot easily be used to compare different runners. It can be used as to track how your running economy is improving over time, though it is also influenced by changes in fitness. Over the weeks and months of training your Relative Running Economy should gradually improve. For instance, I've seen my RRE go from 110-120 to 130-150 over a period of a few months. Sadly, I've also seen my RRE drop when I put on body fat (see Weight Loss and Performance.) This evaluation of my fitness this proved to be remarkably useful to me.

6 Relative Running Economy to detect Glycogen Depletion

Another use for the Relative Running Economy is to compare values within a run. Glycogen depletion will result in a drop in efficiency, and this can be seen in the efficiency value. The glycogen depletion causes more fat to be burned, and fat requires more oxygen to provide an equivalent amount of energy. The graph below shows my efficiency value during a long run, consisting of pacing a 3 hour marathon, then adding on 9 extra miles at a slower pace. You can see my efficiency value staying reasonably constant, with some variation for the hills, until about mile 19. From 19 to 26 you can see my efficiency value gradually dropping due to Glycogen depletion. After the marathon distance you can see some recovery as I refuel somewhat.